Combustion control apparatus



United States Patent O 3,216,661 COMBUSTON CNTRUL APPARATUS Harold T. Sawyer, Los Angeles, Calif., assigner of ten percent to George K. McKenzie and Harry P. Herinner jointly, two percent to Harry P. Heribner, all of New York, NY., and two and one-half percent to Laurence H. Hoerres, Hollywood, Calif.

Filed Oct. 10, 1961, Ser. No. 144,087 1li Claims. (Cl. 236-15) The presently disclosed invention pertains to combustion surveillance :and control systems such as may be useful in large steam power-generating plants, and more particularly, to a unique system for reducing or eliminating the possibility of fuel explosions in the combustion chamber and for reducing pollution of the atmosphere by combustion-chamber exhaust products.

It is known that many serious and costly' boiler explosions are caused, especially during periods of low-load operation and during start-up operations, due to accumulations of explosive mixtures in certain regions in the combustion chamber and ue passages. Such explosions occur from a great variety of conditions, including those attending llame failure, load changes on the system with a resultant loss of accurate control of fuel-air ratio, and situations wherein an excess of fuel is lsupplied under low-load conditions. Sometimes the trouble is caused by chan-ge in the heating-value or B.t.u. content of the fuel, despite the efforts of attendant personnel to maintain proper fuel air ratio. Other causes of such dangerous accumulations of explosive mixtures are known to those experienced in power plant operation.

Heretofore there has been no adequate means or technique to determine incipient build-up of dangerous concentrations of explosive mixtures in a conned space quickly enough to permit either corrective or explosion prevention operations to be carried out, with the result that explosions have occurred. Of course, dangerous accumulations may occur without any ensuing explosion, but the potential hazard to property and life is none the less undesirable.

The present invention provides a system and means for performing rapidly-repeated inspections of known constituents contained in each of one or more locations wherein dangerous concentrations of explosive fuelair mixtures might accumulate, the tests being each completed and repeated in small periods of time of the order of a fraction of a second; and the system and means provides for monitoring of any increase from a conservatively safe concentration toward a dangerous level and for effecting changes that prevent build-up to actually dangerous conditions or concentrations of explosive constituents, The system provides for automatic repeated surveillance of as many regions as may ybe necessary or desired. The testing of the gaseous or other combustible mixtures in each region of interest is accomplished by repetitively examining the region at intermittent short time intervals with a beam of pulsed microwave energy, utilizing techniques and technology known in the microwave spectroscopy arts, and using an electronic data processor or computer to evaluate the results of the repetitive examinations by comparison of the repetitively updated information obtained, with information previously stored in the data store or memory of the computer.

According to the invention a microwave energy generator is repetitively triggered to generate pulses of frequency content selected to include or be limited to that causing resonance in a particular known constituent of interest for example, methane, and the energy is propagated in a beam through a region where dangerous accumulations may occur. Any absorption of energy from the beam is an indication of the presence of the constituent in the region and, of course, the absorption of energy of a particular frequency indicates the presence of that constituent. By proceeding with successive pulses of different `selected frequencies, determinations may be made of the presence of other known constituents of interest. Comparison of energy received after passage of the beam through the region of interest, with a directly measured beam sample, as by means of a comparator means, in each instance furnishes a signal indicative of the abundancy of the respective constituent. The thus derived signals are converted into data compatible with the computer and the data introduced into the computer and there serially compared with sets of stored empirical data previously derived with the apparatus. By these comparisons the computer, under control of a determined stored program, determines at each cycle of the program, the variation from empirical norms derived from previous `analyses and the separation between the existing constituents concentration and one of lowest permissible `danger level. Thus the computer senses any drift away from safe levels of explosive mixtures toward dangerous levels, once at each cycle, and is set to .trigger alarm means and control means if the drift approaches nearer than `a 4determined separation from the lowest permissible dangerous level.

Since microwave operations and computer operations may both be effected with great rapidity, the complete cycles of operations can be effected in respective small periods of time of the order of a fraction of a second. Thus by repetitive successive cyclical operations substantially continuous examination of any region of interest may be accomplished. Also by providing suitable microwave equipment at each site of interest, a plurality of regions of potential danger may be constantly kept under automatic watch. The microwave generator or generators, .an-d the comparator, and other appurtenant apparatus, are controlled by the computer whereby all operations are properly and suitably timed; and the computer is controlled in its operations by a stored program with optional interruption by externally introduced control signals. The construction and arrangement are such that upon sensing of an incipient condition of danger the computer initiates operation of means controlling' the admission of fuel, and of air, into the combustion chamber.

It will be understood that the term material or material of known constituents in this disclosure, is intended as generic to liquid, gaseous and solid materials as well as combinations of these. In the case of solid materials, inspection is desirably performed in a flowing air or gaseous suspension of finely divided portions of the solid material for reasons well known to those skilled in the art of making measurements utilizing electromagnetic wave energy. Liquid materials are desirably processed in an atomized state. It has been determined, and pertinent to the operation of this system, that absorption of microwave energy by liquid or solid particles entrained in air or a gaseous stream, definitely describe their composition when the wavelength of the beam is greater than the particle size.

The preceding, brief, general description of the invention makes it evident that it is a prime object of the invention to provide a system for reducing the danger of explosions in fuel-combustion processes.

Another object of the invention is to provide means for automatically monitoring the products of reaction in one or more regions of interest.

Another object of the invention is to provide means for monitoring incipiently dangerous accumulations of explosive mixtures in a region of interest.

Other objects of the invention will be made apparent in the appended claims and in the following description of a preferred system according to the invention as illustrated in the accompanying drawings. In the drawings:

FIGURE l is a schematic block-diagram showing datasignal channels and control-signal channels, in an array of coordinated physical apparatuses organized and interconnected in accord with the invention; and

FIGURE 2 is a diagram similar in character to FIG- URE 1, illustrating a modified form of system incorporating principles of the invention.

The invention is herein illustratively exemplified in a system for controlling fuel and air input to a boiler in response to concurrent gas-stream inspection in one or more locations within the boiler and contemporaneously supplied data supplied from an external source such as a demand-indicator; a simpler system being illustrated in FIGURE 1 and a more complex and versatile system in FIGURE 2.

Referring iirt to FIGURE 1, there is indicated by ordinal an organization of components comprised in a steam-boiler, including a fuel-inlet means 12, a combustion-chamber 14, a superheater 16, economizer 18, airheater 20, and flue-duct 22, the described boiler being of any suitable and known construction. Fuel of any nature, as for example, powder, liquid, gas or vapor and air mixture is controllably introduced to the combustion chamber by any suitable means, as for example, by burner 12, where combustion is initiated and continues as the fuel burns and products of combustion owing toward ueduct 22 as is indicated by the arrows.

As previously indicated, it is known that different materials in molecular form have different microwave-energy frequency absorption bands or characteristics, and that the extent to which microwave energy of a particular frequency is absorbed in passing through a chemical mass, is a measure of the relative concentration of a particular chemical constituent of the mass to which the constituent is responsive or absorptive. Thus by producing a beam of discrete pulses of microwave energy of selected respective different frequencies and directing the wave energy through various concentrations of each of several possible known constituents likely to be present, sets of data representing presence and relative concentrations of each of the constituents may be obtained. Such data or information are, according to the invention, obtained and entered into the information-store of a digital data-processor of known type, such as an IBM 7071 or other suitable data processor operable to perform operations as hereinafter indicated. Preferably, the data or information thus obtained for the store is accumulated by operation of the system in the exact environment in which the system is to operate. The stored information is used in making comparisons as will later be explained in detail.

As is indicated in FIGURE 1, a microwave generator 24, capable of being selectively keyed to produce microwave energy of each of several predetermined frequencies, is connected by leads 241' to a keyer unit 26 which upon receipt of properly composed signals from a signal line 26i, triggers the generator into operation. The received signals may be, for example, serially arranged binary-coded digital signals and the keyer unit may comprise decoding means of known conventional construction. Alternatively, the decoding means may be included in the arithmetic section 30a of a digital-data processor or. computer 30,- and the signals in that case may be of a type which by magnitude, for example, are effective to cause keyer 26 to initiate sequential production by generator 24 of pulses or bursts of waves of predetermined microwave frequencies.

Generator 24 is coupled to a dual transmitter 32 which comprises suitable radiating means, such as parabolic antenna units diagrammatically indicated at 32a, 32h, to direct respective beams through respective portions of the chemical stream or mass undergoing inspection. The

beams 32C and 32d are not continuous but are in essence each a repetitive timed series of time-spaced bursts or pulses each of a particular selected frequency chosen for determination of a particular possible constituent of the chemical stream. That portion of beam 32C not absorbed by constituents of the chemical stream is received at a first receiver-translator means 34 including an appropriate receptor or antenna Similarly, the unabsorbed energy of beam 32d is received and translated by a similar means 35. The translator sections of means 34 and 35 operate to measure the intensity of the received energy and to convert the measure into binary-coded signals suitable for transmission overrespective leads 340, 350, and reception in input register means forming part of the arithmetic section 30a of computer 30.

Information-processor 30 comprises a program-control section 30C the operation of which is accessible to and governed by a pre-stored program set up in an appropriate set of addresses in the computer data-store or memory, 30s. As is conventional in electronic data processor (EDP) systems, a pre-conceived series of commands is stored in the data-store, individual increments of which can be read out at times determined by the program-control section as cadenced by the computer clock. In response to command, the arithmetic section generates keyer-control signals on lead 261 which are individually effective to initiate keying action `for generation of a burst of microwave energy of a particular frequency to be radiated from a particular one of antenna means 32a, 32h, it being understood that the two antennas are used in rotation. As a burst of energy is radiated and its remnant is received at one or the other o-f receiver-translator means 34, 35, an energy-absorption representing binary signal is transmitted over the appropriate one of leads 340, 350, to an input register that has been readied for the signal by the program-control network in cornputer section 30C. The received signal is serially compared, in sequence, with the previously mentioned stored data and if a favorable comparison or identity is found between the arrived signal and any stored data representinlg an approach to a dangerous concentration of air and combustible material, an alarm circuit 38, 381' is energized to apprise attendant personnel of the existence of a hazardous condition. Concurrently, one or more corrective-action signals are called out from the data store and transmitted on appropriate ones of leads 401', 411 to corresponding ones of fuel-flow controller 40 and airflow controller 41. The latter two means are effective to decode or accept the signals and, in response thereto, initiate fuel and/ or air flow change in the proper sense t0 alleviate the dangerous condition.

Similarly, if the absorption is indicative of a surplus of air (commonly known as excess air for combustion and measured as O2) relative to products of combustion incident to the next following transmission from antenna 32a, that fact is discovered by favorable comparison with the appropriate data read out of the store 30s during the serial comparison, and as a result an appropirate signal is routed over lead 411 to air-flow controller 41 to correct the fuel-air mixture. Thus substantially instantly, during each of rapidly repeated sequences of operation, series of comparisons of the composition of the stream are made and any necessary appropriate action in accord with stored instructions is automatically taken. Since an entire sequence of actions including energy generation and multiple-comparison of empirical data may be effected in a very small fraction of a second, it is evident that not only may optimum stream composition be maintained during normal operation, but potentially dangerous conditions may be detected or anticipated and corrective action initiated before a hazard develops.

While only two beam-paths through the combustion chamber have been indicated (in the interest of brevity and clarity of disclosure), it is evident that as many others may be implemented and utilized as may be necessary or desirable, it being understood that additional capacity within the computer must likewise be provided.

Within the information-processor 30, it will be understood that if the memory provides for only destructive read-out, provision is made for re-inserting all accessed data, to maintain the stored information intact. As is evident, the results of the several comparisons may be presented for sensible purview by conventional digital or analog read-out and translation means; for example, the data may be continuously (or only upon demand being made by an operator) printed by a high-speed printer comprised in the peripheral equipment of conventional EDP systems. Such means are indicated diagrammatically in FIGURE l at 44, the means being connected to the computer by leads 441'.

Also it is evident that preconceived planned changes in the composition of the combustion chamber residue may be made as time passes, by ythe proper insertion of the requisite commands in the data store, and by programming the computer operations for call-out of the changes at the appointed times. And since the explosion-limits (marginal values) of various possible gas/ air liquid/ air or solid/air mixtures are known and can be inserted in the data store for access, the computer can be programmed to institute correction of tendency toward an accumulation of a dangerous amount of combustible or explosive ingredinets in the stream at any section under surveillance prior to an actual accumulation. Thus the actual limits of operation of the boiler, for example, may be automatically controlled.

Further, if desired, cognizance of changes in output demand upon the boiler, incident to turbo-generator demand changes, for example, may be processed and controlled by appropriately programming the computer to periodically interrogate a demand-indicator. Such means are indicated at 46, which is operable to furnish an appropriate signal to a register in the arithmetic section 39a by Way of leads 46o. It is known that sudden changes in demand upon a boiler may cause an unbalance of fuel and air, thus producing dangerous combustion-chamber gas conditions. By appropriate monitoring and surveillance of the demand uctuations, the occurrence of those dangerous conditions may be anticipated by the computer-controlled system, and prevented from occurring.

A more versatile embodiment of the invention is diagrammatically illustrated in FIGURE 2 of the drawings. Generally, system components present in FIGURE 2 and similar to system components present in FIGURE l bear the same number increased by one hundred. For example, a digital data-processor 130 is or may be similar to processor 30 of FIGURE 1. It will be understood that fuel-dow controller 140 and air-flow controller 141 jointly control admission of fuel and air into combustion chamber 114, from which heat is absorbed by such auxiliaries as superheater 116, economizer 118 and air heater 120.

Exemplary microwave generators 124 and 124', each individually keyed or triggered by keyer 126, are arranged for transmission and radiation of microwaveenergy by respective beam transmitters 132 and 132. Keyer 126 is controlled via leads 126i by signals emanating from the arithmetic section 13051 of data-processor 130, in a manner similar to that previously explained. The microwave energy generated is divided between a beam transmitter and a comparator network contained in a comparator unit 160 to which each of the generators is connected by leads as indicated. The unabsorbed energy transmitted via the beams to respective receiver-translators 135, 135' is compared with the previously taken samples in the differential comparison networks of the comparator, and an analog value of the differences, if any, between the samples and the corresponding receiver outputs are transmitted via leads 1600 to an analog-digital converter 162 for conversion to binary digital signal form for impression into an input register means in the arithmetic section 13011 of computer via leads 1620. The data represented by the difference-signals and which represents microwave-energy absorbants in the combustion chamber', are compared serially with sets of stored data read out of the memory section 130s, in a manner previously indicated. ln response to a coincidence between received data and stored data representing an approach to a dangerous condition, such as an increasing concentration of explosive components, the arithmetic section, under the control of program-control system 130e, initiates action of an alarm means 138, and concurrently initiates a programmed change of air supply and/or fuel supply by signals transmitted on leads 141i and 140i, respectively, to the control units 140, 141.

Further, the presently discussed more elaborate system provides for initiating immediate drastic stoppage of air and/ or fuel supply in event of malfunction of the boiler auxiliaries, which causes an immediate or sudden dangerous fuel-air condition to arise. Thus, as each cycle of operations is repeated and the data for that cycle is temporarily stored in a recirculating register for an initial comparison with the next corresponding incoming data, an immediate indication ot' any abrupt change of considerable magnitude is sensed in the comparison, and the value of the change, being in excess of a predetermined value set up in a recirculating register of the computer arithmetic network, initiates transmission of a set of emergency signals to special means. The special means comprise an air diverter-actuator 166 which, incident to reception of an emergency signal or line 166i, immediately actuates air-diverter 166:1 to divert air from the duct 168 supplying the combustion chamber.

Also included in special means 166 is an emergency relay in blower-motor control box 168 which, upon receipt of an emergency signal on lead 1681', causes cut-off of power to the motor driving air supply blower 169. Also, concurrently with the transmission of emergency signals on lines 166i and 168i, the arithmetic circuits in computer 130 generate and transmit on lead 140i an emergency signal elfective to trigger fuel-feed control means to close the fuel-supply regulating valve 140V.

The abrupt change effective to initiate shutting-ofi of fuel and/or `air to the combustion chamber may be initiated by determination of abrupt change toward a dangerous condition either by comparison of microwave absorption changes as previously indicated, or by operation of fuel-ow sensor means, and air-tiow sensor means. For the latter purpose the fuel input line 14th is provided with a flow-sensor 140s eective to provide the computer with an indication of abnormal or excessive fuel flow via line 1400. The air-supply line is provided with an airflow sensor 170s effective to provide the computer with a signal indicative of abnormal or deficient air-flow such as occurs when one of the air-supply components suifers a malfunction. It will be understood that in the exemplary construction, the computer includes means for converting the analog signals produced by sensor means 140s and 176s to binary-coded digital signals, for use in the arithmetic section of the computer.

As indicated in FIGURE 1 and as an adjunct to the analysis of constituent material in the combustion and exhaust passages of a boiler, the system provides means for examining the atmosphere for pollutants. As illustrated, the means is arranged for examination of the cornposition of the exhaust from the boiler; however, as will be evident, the means may be arranged for examination of the extent of pollution of the atmosphere elsewhere. In FIGURE l, microwave energy is supplied by generator 24 to a transmitter 32 of a type similar to one section of transmitter 32. The latter propagates a pulsed beam of microwave energy through the region of interest in the atmosphere, to a receiver-translator means 35. The output data signals of means 35' are transmitted by way of line 3S to the arithmetic section 30a of computer 30, where the information is processed and transmitted by way of a line 49 to a pollution-indicator means 49 for registration. The electrical operations of means 32', 35 and 49 are similar to those of the previousy described similar units and, each being per se known in the arts, will not here be further described. Their operation, timed and controlled by the computer, provides continuous indications of either selected pollutants in the air, or the extent of the pollution.

From the preceding descriptions it is evident that the invention provides means for substantially instantly altering the input of materials including air and fuel, into a combustion process or combustion zone for oxidation or combustion, both in accord wtih predetermined changes ordered by a computer-controlled means according to empirical directives stored in the data store of the computer, and in accord with changes indicated by comparison of results of rapidly repeated series of inspections with data stored in the memory of the computer. Further, it is noted that due to the speed of operation of the system including the computer and the information derived is not by way of sampling but rather is by substantially continuously repetitive instantaneous inspection of the mass or stream itself, adverse changes in the process are substantially instantly detected and immediately corrected. Also, due to the rapidity and the high rate of repetition thereof, the amount of change of constituents per time quantum is normally small and as a result the process may be controlled with extremely close precision. In the event of potentially dangerous conditions commencing during stream start-up or shut-down, or due to malfunction of apparatus, corrective action is automatically taken before the situation reaches an actual state of danger. Similarly, it is evident that the invention as disclosed accomplishes the `other stated objects.

While the particular combustion control method and apparatus herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as defined in the appended claims.

I claim:

1. Apparatus for monitoring and controlling a combustion reaction, comprising: first means, comprising a combustion chamber, and including controllable means for introducing fuel and air to the chamber; second mean, comprising microwave energy generating means, controllably effective to transmit a series of time-spaced pulses of microwave energy in a beam across and through a zone of interest in said combustion chamber; third means, including means for receiving thus-transmitted microwave energy and for comparing the received energy with a sample of non-transmitted energy for producing an output signal representative of the difference in compared values; fourth means, including data-processing means having a data-store and a store of recorded data representing criteria, a program control section, and an arithmetic section, eective to receive the said output signal and effect comparison of values represented by the output signal with values represented by recorded data stored in said data-store and to produce control signals indicative of changes necessary to bring values represented by received output signals into coincidence with stored data; and fifth means, comprising connections from said fourth means to said second means for initiating generation of microwave energy by the latter under the control of said program-control section, and connection from said fourth means to said first means for controlling said controllable means in response to said control signals to produce said changes.

v 2. Apparatus for monitoring and controlling a combustion reaction, comprising: a data-processing system comprising a computer including a data-store and stored data therein; means dening a combustion chamber; controllable supply means for introducing at least air and fuel into said chamber; controllable microwave-energy means effective in response to each of repetitive control signals to generate and transmit microwave energy through material in a portion of said chamber, and for producing signals representative of transmitted energy absorbed by material in said chamber; and means connecting said controllable supply means and said microwave energy means to said computer for supplying said signal to said computer for comparison of the data represented by the signal with said stored data and for transmitting from said computer a control signal to said controllable means for changing the introduction of one or more of said air and fuel to said chamber to bring data represented by said produced signals into coincidence with data stored in said computer.

3. Apparatus according to claim 2, in which said microwave energy means comprise generating means effective to generate discrete pulses of wave energy each of a respective one of wave frequencies determined for resonance with a specific material in said chamber.

4. Apparatus for controlling a combustion reaction, comprising: rst means, comprising a reaction-chamber and controllable means for introducing at least air and fuel to said chamber at variable respective rates; second means, comprising controllable microwave power means, constructed and arranged to pass at least one beam of variable-frequency microwave radiation through at leastv a portion of a zone of interest in said chamber, and to measure any resultant microwave absorption and produce signals representative of the measures of such absorption; third means, comprising electronic data-processing means comprising a data-store with a store of data therein, a program controller and arithmetic means, connected to said first means and to said second means and effective repetitively to perform as steps of a stored program, first, triggering of said microwave power means to produce and radiate radiation of a prescribed frequency composition, second, receive any resultant signal produced by said second means and compare successively the signal with a set of data-representing signals stored in said data store, and third, control with said means in accord with deviations of said signal from stored signals to control introduction of said air and fuel to said chamber in a sense to bring future produced signals toward conformity with stored signals.

5. A system for reducing likelihood of explosion of combustible material in a chamber, comprising: first means, comprising means for generating and propagating a beam of pulses of microwave energy through a region in said chamber, and for receiving a portion of the propagated energy not dissipated in said region and for producing a signal representative of energy dissipated in said region; second means, including data processing means, connected to said first means for controlling generation of said beam and for reception of said signal, said second means being effective to compare data represented by said signal, with stored data and to produce an output signal representative of a known relationship between said stored data and the data represented by said signal; and third means, comprising means for controlling inflow of material into said chamber, connected to said second means for reception of said output signal and responsive thereto to change the inow of material into said chamber.

6. A system according to claim 5, including means responsive to said output signal to produce an alarm signal.

7. A system according to claim 5, including means connected to said second means, for producing a read-out of the data represented by said signal produced by said first means.

8. A system according to claim 5, including fourth means, connected to said second means, effective to propagate microwave energy through a region in the atmosphere susceptible to pollution by combustion products and effective to produce a signal representative of the extent of such pollution, said second means including means to receive said last named signal and to produce a second output signal representing the pollution coeicient as determined by said fourth means; and means connected to said second means for providing an indication of said pollution coefficient.

9. A system for reducing likelihood of explosion of combustible material in a chamber, comprising: rst means, comprising means for generating and propagating a beam of pulses of microwave energy through a region in said chamber, and for receiving a portion of the propagated energy not dissipated in said region and for producing a signal representative of energy dissipated in said region; second means, including data processing means, connected to said iirst means for controlling generation of said beam and for reception of said signal, said second means being efrective to compare data represented by said signal with stored data and to produce an output signal representative of a predetermined relationship between said stored data and the data represented by said signal; and third means, responsive to said output signal and eiective to activate warning signal means as conditions in said chamber approach predetermined undesirable conditions.

10. In combination with steam-generating apparatus having a combustion chamber forming a part thereof and having controllable means for introducing fuel and air thereto; that improvement which comprises microwave energy generating means arranged to transmit time-spaced pulses of microwave energy in a beam across a zone of interest within said combustion chamber for said steam generator, receiving means for said pulse beams including means for comparing the received energy after passage through said zone with that in identical pulse beams bypassing said combustion chamber and producing an output signal representative of the difference in compared values, and data-processing means containing stored data and having an input connected to receive said output signal and operative to compare the same with said stored data and to produce an output signal indicative of changes necessary to bring values represented by received output signals into coincidence with stored data maintained in said data processing means.

References Cited bythe Examiner UNITED STATES PATENTS 1,906,244 5/33 Benjamin 236--14 2,407,838 9/46 Kliever.

2,792,548 5/57 Hershberger 324--5 8.5 2,930,893 3/60 Carpenter et al Z50-43.5 2,967,932 1/61 Edwards et al. Z50- 41.9 3,005,911 10/61 Burhans Z50- 41.9 3,011,718 12/61 Ioerren et al 236-1 OTHER REFERENCES EDWARD J. MICHAEL, Primary Examiner.

ALDEN D. STEWART, Exclrm'ner, 

1. APPARATUS FOR MONITORING AND CONTROLLING IN COMBUSTION REACTION, COMPRISING: FIRST MEANS, COMPRISING A COMBUSTION CHAMBER, AND INCLUDING CONTROLLABLE MEANS FOR INTRODUCING FUEL AND AIR TO THE CHAMBER; SECOND MEAN, COMPRISING MICROWAVE ENERGY GENERATING MEANS, CONTROLLABLY EFFECTIVE TO TRANSMIT A SERIES OF TIME-SPACED PULSES OF MICROWAVE ENERGY IN A BEAM ACROSS AND THROUGH A ZONE OF INTEREST IN SAID COMBUSTION CHAMBER; THIRD MEANS, INCLUDING MEANS FOR RECEIVING THUS-TRANSMITTED MICROWAVE ENERGY AND FOR COMPARING THE RECEIVED ENERGY WITH A SAMPLE OF NON-TRANSMITTED ENERGY FOR PRODUCING AN OUTPUT SIGNAL REPRESENTATIVE OF THE DIFFERENCE IN COMPARED VALUES; FOURTH MEANS, INCLUDING DATA-PROCESSING MEANS HAVING A DATA-STORE AND A STORE OF RECORDED DATA REPRESENTING CRITERIA, A PROGRAM CONTROL SECTION, AND AN ARITHMETIC SECTION, EFFECTIVE TO RECEIVE THE SAID OUTPUT SIGNAL AND EFFECT COMPARISON OF VALUES REPRESENTED BY THE OUTPUT SIGNAL WITH VALUES REPRESENTED BY RECORDED DATA STORED IN SAID DATA-STORE AND TO PRODUCE CONTROL SIGNALS INDICATIVE OF CHANGES NECESSARY TO BRING VALUES REPRESENTED BY RECEIVED OUTPUT SIGNAL INTO COINCIDENCE WITH STORED DATA; AND FIFTH MEANS, COMPRISING CONNECTIONS FROM SAID FOURTH MEANS TO SAID SECOND MEANS FOR INITIATING GENERATION OF MICROWAVE ENERGY BY THE LATTER UNDER THE CONTROL OF SAID PROGRAM-CONTROL SECTION, AND CONNECTION FROM SAID FOURTH MEANS TO SAID FIRST MEANS FOR CONTROLLING SAID CONTROLLABLE MEANS IN RESPONSE TO SAID CONTROL SIGNALS TO PRODUCE SAID CHANGES. 